Process for eliminating porosity in rubber goods.



w. E. PIPER. 'PROCESS FOR ELIMINATING POROSITY IN RUBBEFIl GOODS'.

A l APPLICATION FILED yAUG.2T, 1912. 1,164,860, Patented. Deegzl, 1915.

scrubber fura vi' we 'intuir fr prallhiil@ ltalidlalla @le b WALTER E.PIPER, OF MELROSE, MASSACHUSETTS, ASSIGNDETO BDSION RUBBER SHO COMPANY,l. CBEORATIOI DF MASSACHUSETTS.

success Vron nmmna'rmeronosrrr in RUBBER doens.v

A To all Awhom t moyennes/rn.

Beit known that I, vVilar/ren E. PIPER,

a citizen of the United "States, residing at Melrose,y in the county ofMiddlesex and State of Massachusetts, have invented new vand usefulyImprovements in Processes for Eliminating ,Porosity in Rubber Goods, ofwhich the "following is a specification.

-Mylinvention relates to methods for elim-I wlinating porosity in rubbergoods and rubber stockand the doing away with blisters or .v bubblesbetween the layers-and in the layers before the 'goods are vulcanized;and its 0bjectS are to manufacture rubbergoods in Which rubber is ofuniforml consistency,

'Asolidity and ,grreat'strength` to economize the Vtime and effortAnecessary to produce this result' and to"l produce an article of greatdurability' and Wearing qualities.

' My inventionconsists primarily' in subjecting the rubber parts ofwhich the article l\is, composed,v after the same have been as, Sembledand beforeJ vulcanlzation has takenA place, to a low temperature'for aperiod of 2'5 time sufficient to eliminatefany air bubbles,

` moisture, naphtha yapors or any volatile substances or blisters whichmay be present in the stock, and thereby to produce solidity anduniformity throughout the mass of the My inyehtionfurther consists inthe vari ous modifications and improvements more particularlyhereinafter pointed out `and claimed.

I have found my invention of particular advantage in the manufacture ofrubber footwear there one of the greatest ditliculties heretoforeencountered has been to pro',- .duce uniformly, solid bottoms for bootsand iO-shoes, especially where these .bottoms are thick, or built up ofdi erent layers of stock.

Since the rubber industry began, constant eort' hasl been expended todevise some means of `producing sheets of stock over about twenty-live`thousandths of an inch in thickness` thatlwould be alwaysA solid andfree from'blis'ters after the sheets were vulcani'zed Outside of myprocess this has been possible to a limited degree only, by

vu'lcanizing them under pressure, an'eXpenlsive proceeding and uncertainin results. 1 Where -such pressure is employed, theetfe'ct is to confinethe yolatile-1luids ,in the'stock Specification of Letters Batenlt.Patented Dec, 21, 1915, mation met august 2v, una sesamo. 717,370. l

ever, to free the rubber articles from such -various processesI for the'last Vfourteen years.

I have found from my experience that the vulcanization of rubber dependsupon the -temperature` time, pressure, and percentage of sulfur presentin the rubber to bevulcanized. In order to accomplish a certain specificresult, the other factors beingalike,

`a denite number of. heat units must be introduced in the rubbercompound to accomplish vulcanization. ducedfgradually and slowly asinthe regular dry heat` process, which has been 'in use for sixty years,or they may be introduced sud# These may be intro-A denly and in a verymuch shorter time by placing the goods in receptacles under pressure andworking `athigher temperatures. Vlhere the latter condition exists,there is very much greater danger of damaging the resultingY product byover-vulcanization,

than with the well established slower method.

In steam pressure-cured goods, the tendency to crack and grow brittleupon expo sure to the air is yery much greater than' it is with goodsvulcanized by the regular slow method where the temperature is underbet,- ter-control and vulcanization is not carried out at such a hightemperature orunder,

steam pressure. Pressure, as is well known, mcreases the rate of mostchemical reactions.

I believe myself to have been the first per# son` to haue discoveredthat it is not necessary to apply'pressure at all, and thus I am'enabled to dispense with the expensive form of apparatus required `forthe purpose, and to use an ordinary dry room during-the preliminary heatof the rubber articles produced by this process. By heatingr at a lowtemperature, even in atmospheric air, I have found that there is butlittle danger Aof oxidation. and that in fact, better results'areherebyattained.

In the ordinary course of manufactureshoe bottoms are usually made ofthree distinct partsf-efirst, .what is known' as the s plainsole;second, the tap, which is secured to the forward'part of said sole; .andthird,

rthe heel, which is secured to the heel portion of said sole, adhesivesbeing employed to Sei and to limit their expansion by compression.

cure the aforesaid parts. In assembling the It is the purpose of myinyentiomhowparts, great care has heretofore been eXer-` -1 cisedtopi-event air bubbles or blisters occurring at the line of union of thesame` and even with the greatest caution :I have found that it isimpossible wholly to prevent air bubbles or blisters occurring between`the sui-'faces of the various parts. iThen again, in the joining of theheel to the sole,

. although great'care is used to prevent air ordinaryprocesses thesebubbles.

bubbles or blisters occurring between the heel and.y the sole, it hasbeenfound prac-v tically impossible to eliminate completely by So also',in the formation of the lplain sole and the tap, several layers ofrubber stock are used,

y andl it isa matter of common observation thatV even lwith thethickness of the taps and 'plain soles usuallyemployed, air bubblesand-blisters, though of small proportions, willconstantly occur.

Afterthe bottom has been assembled as above set forth, it is the commonpractice to affix the same -to the rubber boot or shoe by means of somegood adhesive and the completed product is then placed in a closedchamber to be vulcanized, where the said Jproduct is heated for five orsix hours 'at .'a gradual vincrease of temperature from v."aboutv twohundred degree to about two vrber boot l or shoe.

"hundred sixty-five degrees Fahrenheit.l As

aijesultof such heating at such high temperature, any bubblesor minuteair lcells or blisters' whichmay be present ,in the product are'causedto expand to a considerable.,A extent `and to ca'use porosity in thebody of" ythe various component parts ot bottoms manufiwturers of rubberboots and shoes a -largepercentage of seconds isdue to porosity orblisters; andin many of the factoi-ies in consequenceof the demand ofthe trade` rubber heels are nailed througlrthe .bottoni stock in orderto prevent their comi ing loose from the boot orslioe becauseofporosity-or blisters occurring between the top of the heel and the plainsole and in the'plain sole. l

My invention Il believe entirely eliminates i the production of secondsso far as isf concerned porosity or blisters in the stock.

Porosity or blisters are objectionable because of the fact that thewearing qualities of the shoe are greatly impaired that where, blistersoccur between the tap and the `sole A or the heel and the sole, thesoles and thev heels are likely to become detached and that even wherethe best stock is used, the enduring 4qualities of the saine are notmadeso available as inv articles produced through my new and improvedprocess. Tlienagain, with the present processes used in the manufr tureof rubber boots and shoes, there is a marked difference in the qualityof the bottom between that manufactured in summer when the temperatureand humidity are f high andI in the winter when lower temperatures'andless humidity prevail; it being recognized among rubber shoemanufacturers that by reason of such high' temperatiires and humidityin.` the summer time, bubbles :and porosity are much more likely tooccur in the work than in the other` sea-l sons of the' year whentemperature and hulinidity are lower.

llife chief advantages of n'iy'i new process are, first, that a uniform.result in all shoe bottoms, -whether made .of better or cheapermaterial is obtained;;second, thatfthereare no seconds from porosity, orblisters;

third, that no separations occur of `theh'eelv or tap and the sole dueto defective yheel or tap or sole making; fourth, that the wearingqualities of the shoebottom are bettered to an extent of double that ofthe ordinary shoe bottom.; fifth, that a'much betterarticleean be madeout of cheaper stock than heretofore; sixth,th at vmy process can' be.appliedto all xgrades ofvrubber footwear;

seventh, that my process can -be used to advantage in all arts where itis found desii-able to make solid rubber stock eighth,

that no great expenditure of moneyY or time is necessary in utilizing myprocess; and ninth, that my process, as is obvious, can

be used in other ways and manners,

vAttentionis hereby directed to the drawing in which similar numeralsofA designation refer to similar parts throughout 'the several views.

Figure l is a longitudinalsection ofa rubber boot or shoe such asis"lcommonlyv .now-sold ontlie market showing porosity and blisters -in theshoe bottom. Fig. 2 is a longitudinal section of a shoe bottom beforethe samehas been subjected to my process.

process and` showing the uniform character ofthe shoe bottom. v g IReferring 'to ythe dra\`ving.`to'the plain rubber sole 4, l affix, bymeans of some, good adl'iesive, the'rubber heel 5; and the' rubber tap"(3 to the'under portion thereof; Upon vthe'upper surface of said plainsole 4, I

aiiix the form of frictioned sheeting l1. 'lliese parts so assembledconstitute what -is termed in the art as t-he bottom and I have.

designated the same as an entirety by the -nunieral lO. Where a bottomis constructed `1.15 Fig. 2 is a longitudinal section of. -a shoe y towhich the sole shown in Fig. 2 has vbeen applied after having beensubJected to my.

niemeer) of a single'sole, then as is obvious the heel and the tap 6 maybe dispensed with and Vthe exposed surface of said sole 'knurled 'orcorrugated inanyof the Ways Well known 1n the art of manufacturingrubber boots and shoes. By the term bottojmtherefore,

I desire to be understood as referring to any i end all structures ofrubber which serve as grec of care isunnecessary.

joint insecure andpreventa firm union ofV the parts; but with my processsuch a de- After the parts composing 4the bottom have been assembled, asabove described, I

then place the same in a chamber Where the bottoms arev subjected torelatively' low temperature sufficient to eliminate all air,

naphtha and other gases'which may be in the stock for various causes orwhich may be between thelayersof `stock as above referredl to; By actualvexperiment for a period of over six months I have found that thetemperature which is the most advantageous for my process 1s between onedegrees Fahrenheit and that about thirty'- six hours is the time`re'quired. Care hast-o be exercised that the temperature is not' carriedto such an extent as to produce vulcanization.

The temperature Which I employ, I have found bears Within certain limitsa ratio to the period of time during which the shoe .'bottom is warmedor heated. In other Words, a temperature lower than between one hundredand thirty and one hundred thirty-ve degrees Fahrenheit may be employedprovided lthat lthe shoe is heated a correspondingly longer period oftime but' the range of temperature which is amenable to my proess iscomparatively Ysmall sothat the corresponding period of time needed whena lower or higher temperature is 'employed than between one hundredthirty and one hundred thirty-live degrees Fahrenheit is not great.' Ihave found by experiment' that the most advantageous results secured as'above stated are when the temperature is between one hundred and lthirty, and one hundred thirty-five degrees Fahrenheit.

After the bottoms have been subjected' to the steps of -my process asdescribed above, they are then secured to the layers 12 of the upper{Vof the rubber shoe or boot in the ordinaryzmanner, and the entire'shoe or boot. is placed .in the vuleanizing chamber and thelshoe is'vulcanized." `A`fter i vulcanization has taken place, I have found that'the shoe bottoms are a solid product, and .that there are substantiallyno blisters uct Where a uniformly hundred thirty. and one hundredthirty-live or bubbles between thelayers and substantially no porosityin the rubber itself.

In the usual course of. manufacture I have found it more economical,Where a single rubber shoe'sole was used, to subject the stock before,said shoe soles are cut out to the process above described; but I alsohave produced. good results by .treating the said Vshoe soles after theyhave been cut. In the case of bpttoms -:tor rsolid heel goods, whichhave a plain sole and tap anda heel as-above described, I find thatIiobtained the best results after the bottoms have been assembled. Theessenceof my invention, or discovery, resides in the fact that intheprocess the gases and volatile fluids are substantially lexpelledVbefore vulcanizatiom 4without the use of pressure; and at the same-.;time causing the particles of the stock to come closely together; sothat after Vulcan- 'iz'atiom lthe resulting product is solid, nonporous.i

lVhile I have described'my invention With particular reference tothemanufacture of boots and shoes, I do not desire to limit the -same tosuch applicatiomit being obvious lthat my invention could bey used toadvana temperature below that of vulcanization,

and atmospheric pressure irrespective of that'which may be due to thesurrounding air and gases caused by said temperaturev until all fluidsoccasioningporosity insaid stock have. been substantially removed, and.

. thereafter 'vulcanizing said bottom.

2. A process for producing a uniformly solid rubber bottom for a rubbershoe, consolid mass ofrubber' sisting in constructing a shoe bottomdirectly of layers of calender-sheeted vulcan izableplastic to'substantially its linal form, and in heating said shoe bottom subsequentto its formation at a'temp'erature below that of vulcanization, andatmospheric pressure irrespective otthatwhich may be due to theexpansion of the `surroundingair and gases caused by said temperatureuntil all fluids occasioning porosity in the joints and layers of saidbottom have been substantially removed, and thereafter vulcanizingI saidbottom.

"3. A process for producing a uniformly solid rubber bottom for a rubbershoe, consisting in assembling the parts of a shoe bottom constructed ofcalender-sheeted vulcanizable plastic' to substantially its final formand then subjecting the same. subsequent to itsiormntion at ntmosphericpres- ,sure irrespective of that which muy be due to the expnnsionof thesurrounding ga'ses 'mused by the surrounding temperature to u degreeofvhent during u period of time sufficient to expel the free gases insaid bottom lwithout vhlcunizing the' sume, land thereafter subjectingthe completedlstructure to 'vulcunizutlon 4. A process for producing auniformly y solid rubber bottom for u rubber shoe, conslstlng 1nconstructing a bottom of celen- 1,164,s6o i l dered rubber, and thensubjecting the same In testimony whereof I have hereunto set i, 20

my hundin presence oitwo subscribing witnesses, this 24th day of August1912.

4`WALTER E. PIPER. W- tnesses Ronlz'r JACKSON CRAM, y y ELIZABETH S.OVCONNOR.

